satip/s400: Support carrier freq offset correction

It is not unusual to have an LNB with LO frequency offset exceeding the
regular DVB-S2's coarse frequency offset estimation range. Hence, in
some cases, it is preferable to tune to a center frequency with a fixed
offset relative to the nominal value. This patch adds such an option
(named --freq-corr) on the satip and standalone receiver commands. With
the sat-ip receiver, the frequency correction has to be specified every
time on the launch command (blocksat-cli sat-ip). Meanwhile, with the
standalone demodulator (Novra S400), it has to be specified once on the
configuration step (blocksat-cli standalone cfg).

blocksatcli/satip.py

@@ -80,14 +80,20 @@ def _assert_addr(self):
             raise RuntimeError("Sat-IP device address must be discovered or "
                                "informed first")
 
-    def set_dvbs2_params(self, info, target_modcod):
-        """Set the DVB-S2 and MPEG TS parameters of the target stream"""
+    def set_dvbs2_params(self, info, target_modcod, freq_corr):
+        """Set the DVB-S2 and MPEG TS parameters of the target stream
+
+        Args:
+            info (dict): User info dictionary.
+            target_modcod (str): Target MODCOD.
+            freq_corr (float): Frequency correction in MHz.
+        """
         modcod = _parse_modcod(target_modcod)
         pilots = 'on' if defs.pilots else 'off'
         sym_rate = defs.sym_rate[info['sat']['alias']]
         self.params = {
             'src': 1,
-            'freq': info['sat']['dl_freq'],
+            'freq': info['sat']['dl_freq'] + freq_corr,
             'pol': info['sat']['pol'].lower(),
             'ro': defs.rolloff,
             'msys': 'dvbs2',
@@ -452,7 +458,8 @@ def _find_serving_frontend(self, active_frontends):
             except ValueError:
                 continue
 
-            if fe_freq == self.params['freq'] and fe_pol == self.params['pol']:
+            if fe_freq == round(self.params['freq'], 2) and \
+                    fe_pol == self.params['pol']:
                 candidate_frontends.append(fe)
 
         # If there is only one matching frontend, it's got to be ours.
@@ -659,6 +666,10 @@ def subparser(subparsers):
                    metavar='',
                    help="DVB-S2 modulation and coding (MODCOD) scheme. "
                    "Choose from: " + ", ".join(defs.modcods.keys()))
+    p.add_argument('--freq-corr',
+                   default=0,
+                   type=float,
+                   help='Carrier frequency offset correction in kHz')
     p.add_argument('-u',
                    '--username',
                    default=DEFAULT_USERNAME,
@@ -761,7 +772,8 @@ def launch(args):
             return
 
     # Tuning parameters
-    sat_ip.set_dvbs2_params(info, args.modcod)
+    freq_corr_mhz = args.freq_corr / 1e3
+    sat_ip.set_dvbs2_params(info, args.modcod, freq_corr_mhz)
     url = "http://" + sat_ip.host + "/?" + urlencode(sat_ip.params)
 
     # Run tsp

blocksatcli/standalone.py

@@ -381,13 +381,19 @@ def print_demod_config(self):
                     print("- {}: {}".format(label, val))
         return True
 
-    def configure(self, info):
-        """Configure the S400"""
+    def configure(self, info, freq_corr):
+        """Configure the S400
+
+        Args:
+            info (dict): User info dictionary.
+            freq_corr (float): Frequency correction in MHz.
+
+        """
         logger.info("Configuring the S400 receiver at {} via SNMP".format(
             self.address))
 
         # Local parameters
-        l_band_freq = int(info['freqs']['l_band'] * 1e6)
+        l_band_freq = int((info['freqs']['l_band'] + freq_corr) * 1e6)
         lo_freq = int(info['freqs']['lo'] * 1e6)
         sym_rate = defs.sym_rate[info['sat']['alias']]
         if (info['lnb']['pol'].lower() == "dual"
@@ -519,6 +525,10 @@ def subparser(subparsers):
                     action='store_true',
                     default=False,
                     help="Print all commands but do not execute them")
+    p1.add_argument('--freq-corr',
+                    default=0,
+                    type=float,
+                    help='Carrier frequency offset correction in kHz')
     p1.set_defaults(func=cfg_standalone)
 
     # Monitoring
@@ -588,7 +598,8 @@ def cfg_standalone(args):
     if (not args.host_only):
         util.print_header("Receiver Configuration")
         s400 = S400Client(args.demod, rx_ip_addr, args.port, dry=args.dry_run)
-        s400.configure(user_info)
+        freq_corr_mhz = args.freq_corr / 1e3
+        s400.configure(user_info, freq_corr_mhz)
 
 
 def monitor(args):